Lock seam for sheet metal pipes



Dec. 30, 1958 J. G. BRATSCH 2,866,481

- LOCK SEAM FORHSHEET METAL PIPES Filed Feb. 18, 1957 I N VEN TOR.

LOCK SEAM FOR SHEET METAL PIPES Jesse G. Bratsch, Minneapolis, Minn., assignor to Char- Gale Manufacturing Company, Anoka, Minn., a corporation of Minnesota Application February 18, 1957, Serial No. 640,648

4 Claims. (Cl. 138-74) My present invention relates to improvements in lock seams for sheet metal pipes and more particularly to lock seam constructions wherein during assembly of the seam the adjacent edges of the blank from which the pipe section is formed may be progressively interlocked from one end of the pipe section blank toward the other end thereof.

- Among the important objects and advantages of the invention are the following:

The provision of an improved lock seam construction of the progressive type which is relatively inexpensive to manufacture, can be assembled with a minimum of effort and time, and which, when assembled, will provide a neat smooth seam wherein the interlocking of the joined edges is exceptionally positive and exceptionally air tight.

Progressive lock seams of the class in question generally comprise a substantially continuous lock shoulder on one of the adjacent-longitudinal edge portions of the pipe section and a series of spaced lock detents on the opposite longitudinal edge portion of the blank for progressive and successive engagement with the said lock shoulder of the opposite edge portion; this progressive locking engagement of the opposite edges of the blank forming the pipe section facilitating the assembly of the join or seam which is generally assembled on the job rather than at the factory where the seam contours were preformed. One of the disadvantages of prior art progressive lock seam constructions of this character has been the fact that the spaced lock detents have been relied upon not only as an aid in assembling the seam but also as the sole means for subsequently maintaining the seam locked closed against unwanted separation and against air leakage. Such lock seams have often been referred to as button seams for the reason that the detents, sometimes referred to as buttons, are usually located several inches apart. Obviously, such seams have the disadvantage common to any button seam, namely, a relatively wide spacing between points of anchorage or fastening, which means that such a seam is relatively insecure and less immune to air leaks than would be the case if the opposite edge portions of the sheet forming the pipe section were in continuous interlocking engagement, for example. It is, therefore, an object of the instant invention to provide an improved lock seam of the general character described involving spaced detents which may be progressively engaged during the assembly of the seam to facilitate such assembly but wherein there are relatively long and relatively straight edge portions lying between adjacent detents or buttons which become interlocked with a substantially straight and continuous lock shoulder formed on the other edge portion of the sheet when the assembly has been completed. Since the spaced lock detents or buttons need occupy but a small percentage of the length of a scam in my novel construc-.

tion, it will be clear that the seam, when finally assembled, can provide for nearly complete locking engagement between adjacent edge portions of the blank, thereby providing a lock seam giving maximum mechanical and pneumatic security.

The above and still further objects and advantages of my invention will be apparent from the following specification, appended claims and attached drawings.

In the accompanying drawings, which illustrate the invention, like characters indicate like parts throughout the several views:

Referring to the drawings:

Fig. 1 is a fragmentary perspective view of a section of sheet metal pipe blank embodying the seam construction of the instant invention but illustrating the same befor assembly of the seam; I

Fig. 2 is an enlarged fragmentary sectional view takenon the line 2-2 of Fig. l; t

Fig. 3 is a sectional view corresponding to Fig. 2 showing the seam assembled; and

Fig. 4 is a fragmentary sectional view taken on the line 4-4 of Fig. 2.

Pipe sections of the kind illustrated are most commonly used in connection with heating or cooling systems to conduct heated or refrigerated air as the case may be, but, of course, have many other applications. Each such section is formed from a generally rectangular sheet of metal such as steel, aluminum or the like. In the drawings a blank for one such pipe section is indicated as an entirety by 1. These pipe sections are manufactured in varying lengths, generally from two to eight feet more or less each. While the blanks are still in fiat condition the opposite longitudinal marginal edge areas thereof, indicated respectively by the numerals 2 and 3, are formed to provide opposite interlocking sections of what will become the seam upon assembly, and thereafter the flat sheets are rolled into nearly, but somewhat incomplete, cylindrical form shown in Figs. 1 and 2. Generally the pipe sections are shipped from the factory and to the place of installation with the seams open as shown in Figs. 1 and 2; the assembly of the seam being generally completed by the workmen on the job. One of the ad vantages of shipping in this seam-open condition is that it permits telescoping of a number of sections together to reduce the overall bulk of the shipment and packing problems.

In the preferred arrangement shown in the drawings, one longitudinal marginal edge area of the pipe section blank 1 (the lefthand edge area in Figs. 1, 2 and 3) comprises a first portion 4 folded over circumferentially backwardly and radially inwardly upon itself throughout its length to define a straight folded longitudinal edge 5. In a plane generally parallel to but circumferentially backwardly spaced from the plane of the folded edge 5 the first portion 4 is folded over circumferentially forwardly and outwardly to define a second folded edge ,6 and a circumferentially forwardly extending lock flange 7 which extends forwardly beyond the plane of thefolded edge.

5 and is radially spaced from the first portion 4 which connects the folded edges 5 and 6 to define therewith a longitudinally extending outwardly opening channel 8, for reception of the other longitudinal seam-forming edge area of the sheet indicated as an entriety by 3. The free edge portion of the lock flange 7 is folded radially outwardly and circumferentially backwardly. upon itself throughout its length to define a folded longitudinal marginal edge 9 and a rearwardly facing longitudinal edge disposed generally parallel to the edges 5, 6 and 9, which provides a continuous lock shoulder 10 in circumferentially spaced generally parallel relation to the edges 5 and 6 but circumferentially forwardly spaced from the edge defined by the fold 5.

The other marginal seam-forming edge area of the.

sheet, indicated by 3, is first, radially inwardly offset, and.

then, in the preferred form illustrated, circumferentially backwardly and radially inwardly folded upon itself to define a folded longitudinal marginal edge 11 adapted to be received in the channel 8, and a circumferentially rearwardly extending flange 12 terminating in a circumferentially rearwardly facing longitudinally extending lock edge 13 generally parallel to but circumferentially rearwardly or backwardly spaced from the folded edge 11 and also radially inwardly spaced from that part of the edge area 3 that is immediately backwardly adjacent the radially inwardly offset portion of the edge area 3. This last said lock edge portion 13 is formed to provide, at longitudinally spaced intervals therealong, a series of spaced detents or buttons 14 adapted to progressively and successively engage the lock shoulder 10. In prac-- tice, these detents 14 are generally quite widely spaced apart, three inches more or less for example. Since these detents are each relatively very small, it will be obvious that they collectively occupy but a small percentage of the total length of the seam.

In the preferred embodiment of the invention illustrated, the lock detents or buttons 14 are formed by the simple expedient of transversely slitting the flange 12 through the lock edge 13 and then bending downwardly or radially inwardly the edge portion immediately adjacent one side of the slit, all as shown best in Fig. 4. As best shown in Figs. 2 and 3, the lock shoulder is radially spaced from the adjacent portion of the lock flange 7 by a distance approximately equal to the depths of the detents 14 in a direction radially of the pipe section so that the straight portions of the lock edge 13 between the spaced detents will, upon final assembly of the seam, be in directly opposed interlocking edgeto-edge abutting relationship with the lock shoulder 10.

During the process of assembling the blank 1, the detents 14 are progressively successively engaged with the lock shoulder 10 working from one end toward the opposite end, but when the assembly of the seam is complete, as shown in Fig. 3, the lock detents or buttons 14 will be disposed radially inwardly of the plane of the lock shoulder 10 (below the shoulder 10 in the drawings) and the lock straight portions of the edge 13 lying between the several detents 14 will, as previously indicated, be disposed in directly opposed face-to-face abutting relationship with the lock shoulder 10 so as to provide nearly complete interlocking engagement between the opposite longitudinal edge portions of the sheet. By virtue of this fact, my improved seam construction provides greater mechanical security and a better air seal than has hitherto, to the best of my knowledge, been accomplished by progressive lock seams of the prior art.

While I have shown and described a commercial embodiment of my novel lock seam for sheet metal pipes, it will be understood that the same is capable of modification without departure from the spirit and scope of the invention as defined in the claims.

What I claim is:

l. A sheet metal pipe blank of generally cylindrical shape having opposed marginal seam-forming longitudinally extending edge areas, one of the edge areas having a longitudinally extending circumferentially forwardly projecting lock flange and a longitudinally extending circumferentially rearwardly projecting and rearwardly facing lock shoulder radially outwardly spaced a given distance from the lock flange and defining therewith a 1ongitudinally extending outwardly opening channel, the other edge area having positioning-locking means for progressively and successively engaging the lock flange of the said one edge area to facilitate the assembly of the blank into a pipe section and then retaining the pipe section in the assembled condition, said positioning-locking means including a longitudinally extending folded marginal edge portion having a circumferentially rear wardly extending flange terminating in a circumferennally rearwardly facing lock edge radially inwardly spaced from a part of the said other edge area, said lock edge having, at space intervals therealong, oflset portions defining longitudinally spaced detents, said detents each being oflset radially inwardly from the lock edge a distance substantially equal to the said given distance of the radial spacing between the lock flange and the lock shoulder of the said one edge area, the portions of the lock edge intermediate the detents being substantially continuous for engaging the lock shoulder of the said one edge area in edge-to-edge abutting relationship when the said other edge area is received within the channel of the said one edge area with the detents being in engagement with the lock flange of the said one edge area.

2. A sheet metal pipe blank of generally cylindrical shape having opposed marginal seam-forming longitudinally extending edge areas, one of the edge areas having a radially inwardly extending circumferentially forwardly projecting lock flange and a circumferentially rearwardly facing lock shoulder, said lock shoulder being radially outwardly spaced from the lock flange and defining therewith a longitudinally extending outwardly opening channel for reception of the other marginal seamforming longitudinally extending edge area, the said other edge area having a circumferentially rearwardly extending flange terminating in a circumferentially rearwardly facing lock edge, said lock edge being radially inwardly spaced from a part of the said other edge area and having at space intervals therealong offset portions defining longitudinally spaced detents adapted to engage the said lock flange of the said one edge area to position the lock edge of the said other edge area in edge-to-edge abutting engagement with the lock shoulder of the said one edge area when the said other edge area is received within the channel of the said one edge area.

3. The structure defined in claim 2 wherein the said radial spacing between the lock shoulder and lock flange is substantially equal to the maximum offset of the detents from the lock edge, the portions-of the lock edge lying intermediate the detents being substantially continuous and straight, whereby the detents may be progressively and successively engaged by the lock flange to facilitate the assembly of the blank into a pipe section with the portions of the lock edge lying intermediate the detents being aligned with and in edge-to-edge abutting locking engagement with the lock shoulder of the said one edge area upon completion of the assembly.

4. A sheet metal pipe section blank of generally cylindrical shape having opposed marginal seam-forming longitudinally extending edge areas, one of the edge areas comprising a first portion folded over radially inwardly and circumferentially rearwardly to define a straight folded longitudinally extending edge and a second portion folded over radially inwardly and circumferentially forwardly to define a lock flange projecting circumferentially forwardly beyond a radial plane passing through the edge defined by the first fold, said lock flange being radially inwardly spaced from the said edge of the first fold and defining with the first and second folds a longitudinally extending outwardly opening channel for reception of the other edge area, the free edge portion of the lock flange being folded radially outwardly and circumferentially rearwardly to define a circumferentially rearwardly facing lock shoulder radially outwardly spaced from the lock flange, the said other edge area being radially inwardly and circumferentially rearwardly folded to define a circumferentially rearwardly extending flange terminating in a circumferentially rearwardly facing lock edge disposed radially inwardly from a part of said other edge area, said lock edge having at space intervals therealong offset portions defining longitudinal- .ly spaced detents adapted to engage the lock flange of the said one edge area to facilitate the assembly of the blank into a pipe section, said radial spacing of the lock shoulder relative to the lock flange of the said one edge area being substantially equal to the maximum offset of the References Cited in the file of this patent UNITED STATES PATENTS Sladky Mar. 7, 1933 Siebenlist Apr. 21, 1936 Kinghorn' et al June 5, 1956 Curtis July 31, 1956 

